FD3S RX7

[The Dark Side of Will]

I don't disagree that it would make a hell of a track machine. I just like the way a mid-engine car handles. quote]

I think my mid-engine experience was ruined by going from an Skyline GTR to a Fiero. The fiero felt like a boat swinging back and forth, understeering like crazy. If I raced the fiero first I would probably have a lot better things to say about it. If I built an 88 first I probably would have been happier with it.

An Iron block datdun is going to be a little different than an aluminum block FD. The FD is a lot more rigid, probably shorter and the engine will weigh quite a bit less. I like the fact that the FR layout is much easier to control at the limit. Something you think about when going through high speed corners lol...

The '88 front helps a LOT. The Fiero to which I was comparing my dad's Datsun was my '86 SE into which I had transplanted an '88 front suspension.
Being F/R doesn't have much to do with controllability at the limit. That's suspension design.
The Datsun and FD have similar engine positions relative to the front wheels.
I can't speak to chassis stiffness because I don't know any numbers for the Datsun.

I have driven an (rotary powered) FD and been fairly spirited... although I haven't spent much time at the limit with it. It's certainly a world class chassis and the foundation of a kickass car. To me it still felt and responded like a front-engine car; hence my lament that there's no equally accessible and capable mid-engine car.
Maybe I'll go test drive an NSX when I get back. A contractor at work has one... maybe I can bum a ride off him by offering to trade drives in the Fiero... yeah right.

[The Dark Side of Will]

that $32k would get you an NSX or maybe a good used F355. Certainly a good used 328 Ferrari. Add forged pistons and nitrous, they might be close enough. IDK. I'm still trying to find an '84 'vette with the optional suspension that had the ultra stiff springs.

I'd always heard that NSX's sound good... but WOW... http://www.youtube.com/watch?v=oc2-VNbnQvI

[darkhorizon]

NSX and lotus are fun, but honestly in today's world of horsepower, they are just a bit lacking overall. The local lotus's are really sick while going around on-ramps after 6-8k was dumped into the suspension package, but the 4-5k in the motor still barely puts them in the mid 12's 1/4 mile wise. I had a run with one of them on the eway a few months ago while I was in the fiero. I could pull up a few bus lengths on the straights going 130+, but he could take ramps that I could barely handle at 70, at 100+... Absolutely sick chassis.

The few NSX's i have cruised with never really got too crazy, but i would say that alot of their prowess is in their ability have a pretty high powerband (pretty fast roll racing cars it seems), as they were pretty darn fast otherwise for what they were.

I take it everyone forgot about MK4 supras? Remember they are STILL the kings of power per dollar in import performance cars. 700RWP with just a turbo, cams, and engine management? Giant factory brakes and rims, decent factory suspension... hell ill take it. They PLUMMETED in price the last few months... autos that were almost 20k this last summer, could be had for nearly 4 digits now. (I am speaking about TT supras only btw,I could only imagine how cheap the nonT cars are getting)

The built cars are typically cheaper, and offer up more performance in the longrun, as well as you get the satisfaction of building it.

FD's are pretty sweet, and the horsepower goes a very long way... can be very fast for very little as stated.

The T56 is going to be the obvious choice as well IMO.

I wouldnt be COMPLETELY afraid of the iron blocks as well... You get quite a bit more horsepower out of the box (LQ9 makes more HP than a LS6/LS2, LQ4 is in the same range as the LS2), but on top of it being 40-50lbs heavier, you have to still swap on the shorter LS intakes.

[The Dark Side of Will]

The point of the NSX was never horsepower. After all, Ayrton Senna was the development test driver. The first year only had 250 HP.

The Elise doesn't need a lot of power. It's not build to be a drag racer. I saw a video of one with a built engine and turbo pushing 450 HP on a road course. It would spin out as soon as the turbo spooled.

Supras are nice, but they're heavy. The FD is at least as capable a chassis and 800 lbs lighter.
I have been musing about a 1FZ-FE swap from a Land Cruiser into a Slowpra to help deal with the heft.

Since when is 16x8 huge? Grand Prix had those in the early 90's. C4 Vettes may not be popular, but they're getting pretty cheap and are easy to make fast also.

The iron blocks are about 80#'s heavier than the aluminum.

[darkhorizon]

Since when is 16x8 huge? Grand Prix had those in the early 90's. C4 Vettes may not be popular, but they're getting pretty cheap and are easy to make fast also.

All Turbo supras came with 17x9.5. We run a slightly taller than stock 315 ET street on them.

I sold a 92 C4 last year for 3900. It ran and drove, had some minor dings and chips all over, fairly faded paint (I would really have had to do a full repaint on it), had some damage inside as well. I was really not feeling that car myself.. it was a giant MEH on the performance department with that crummy relic under the hood.

The iron blocks are about 80#'s heavier than the aluminum.

While that seems to be the "on paper" number, I have also seen a few posts on LS1tech suggesting it is a bit less than that when comparing apples to apples. I could be wrong though.

[crzyone]

I take it everyone forgot about MK4 supras? Remember they are STILL the kings of power per dollar in import performance cars.

To get 700hp out of a supra isn't "cheap". The turbo or turbos, manifold, fuel system, intercooler, piping etc etc adds up fast. I know, I went through it with my GTR. Difference is my engine is fully built as well.

Anyways, I'd much rather have an LS FD than a supra or even a skyline. There is the fun factor to consider with a small tossable car with a large powerband. My GTO is fun, but you feel the weight of it. Same powertrain in a car that will weigh atleast 1000lbs less will be awesome. Plus, you can't beat the soundtrack. A little FD making NASCAR sounds is going to be very cool.

http://www.youtube.com/watch?v=e0U01m9p-ww

[The Dark Side of Will]

What about V8'ing your Skyline? It's between the FD and GTO in weight. With the AWD it'll put power down better than either. The real plus is that you already have it.

[Atilla the Fun]

Skip the T56. It's heavy. Instead, get a Tremec TKO 600. Ratios are 2.87/1.89/1.28/1.00/OD, which is a choice between either 0.82 or 0.64, and these are far lighter and somewhat smaller than the T56. If you want even lighter, even smaller, and way more choice of ratios, including first gears in the 2.5:1-2.4:1 range, try D&D or Astro for their maximum effort T5s. These will hold over 450 ft-lbs, and over 550 HP. About what a cam-and-heads-LS1 will make.

Do these transmissions have the same insanely tall 6th gear? I want this car to get good fuel mileage on the highway as well. How about mounting, same as a T56, like a direct swap?

Only reason I'd go T56 is because they are cheap and plentiful. I do like the idea of a lighter transmission though.

Since you're gonna grenade the stock diff assembly anyway, and have to replace it with either a 'vette or Cobra unit anyway, you may as well. After all, 25" tires, a 4.30:1 diff, and a 2.66:1 first makes first useless. You'd still have only 5 useful forward gears. T56s are not cheap, even used. So, get an aluminum-case, 31-spline 8.8" Ford diff assembly, as used in the Cobra and that can have gearing as tall as 2.73:1, and deeper than 5:1. Plus way way WAYYYY more choices of differentials, most of which are cheaper than any RX7 diffs anyway.
As for attaching these other transmissions to your engine, it's so easy a baby monkey could do it. With the T56, you hafta use hydraulic clutch release, while with the others, you have the other options of mechanical or cable mechanisms, as well as hydraulic. All offer VSS outputs, but the used production T56s don't offer mech. speedo outputs. These others do.
I am very very anti-T56, as you might be able to tell. Plus, if you put any popular cam in a fourth gen with the LS1 and T56, you can't use sixth anymore unless you change the axle ratio, and there goes the 31 mpg on the highway. You should expect a 5.7L LSx to give 27 mpg if you gear it to turn 1800 rpm at 65 mph. That 31 mpg stock is with it geared for 1450 rpm at 65 mph.

[Atilla the Fun]

Back to the engines. The iron block vs aluminum block weight difference depends on which versions. If we use the original 5.7L LS1 aluminum block as the baseline, the iron 4.8/5.3 block is about 88 pounds heavier, while the iron 6.0L block is about 65 pounds heavier, a difference of 23 pounds. This is because of the common water jacketing, giving the 4.8/5.3 block some extraordinarily thick cylinder walls, of denser iron than the old SBC blocks. As to power levels, the iron blocks will hold way more power, but stock, they never made more power than any corvette version. The LQ9 offered 345 hp, same as the original LS1, but that's as close as it got while still making fair comparisons. Comparing the LQ9 to the Camaro LS1's 305+ hp isn't fair, because the trucks and 'vettes both had free-flowing exhaust and inlet systems, while even the SS & Ram-Air versions in the F-cars did not. If you can be happy with 800 crank HP at sea level, the aluminum block is the way to go. But beyond that, go iron block.

[crzyone]

LS1 is 50lbs heavier than the 13b, don't want to add even more weight with a cast iron block.

On ebay I can get an LS1/T56 combo for $2500. That is the route I'll be taking.

[crzyone]

What about V8'ing your Skyline? It's between the FD and GTO in weight. With the AWD it'll put power down better than either. The real plus is that you already have it.

It has never been done while keeping the AWD and I don't really want to be the first to do it either. The car is fine the way it is for racing, just sucks around town.

My GTR is 3000lbs right now, completely gutted, no A/C and as soon as I take out my HICAS all wheel steering and put in the lock bar I will be saving another 80lbs. The GTR is really light weight for what it is.

[The Dark Side of Will]

As for attaching these other transmissions to your engine, it's so easy a baby monkey could do it. With the T56, you hafta use hydraulic clutch release, while with the others, you have the other options of mechanical or cable mechanisms, as well as hydraulic. All offer VSS outputs, but the used production T56s don't offer mech. speedo outputs. These others do.

This is like saying that an engine is really cool because you can rip off all that EFI crap and install a carb... We're not talking about stone age muscle cars with cable clutches and mechanical speedometers. We're talking about a '90's Japanese supercar. Heck, the 300ZX had a vacuum booster for the clutch hydraulics.

I am very very anti-T56, as you might be able to tell. Plus, if you put any popular cam in a fourth gen with the LS1 and T56, you can't use sixth anymore unless you change the axle ratio, and there goes the 31 mpg on the highway. You should expect a 5.7L LSx to give 27 mpg if you gear it to turn 1800 rpm at 65 mph. That 31 mpg stock is with it geared for 1450 rpm at 65 mph.

If you're camming the engine, you're not concerned about the 31 mpg anyway. I thought the hot ticket in a T56 car (F or Corvette) was a 4.11 rear?

[Atilla the Fun]

As for attaching these other transmissions to your engine, it's so easy a baby monkey could do it. With the T56, you hafta use hydraulic clutch release, while with the others, you have the other options of mechanical or cable mechanisms, as well as hydraulic. All offer VSS outputs, but the used production T56s don't offer mech. speedo outputs. These others do.

This is like saying that an engine is really cool because you can rip off all that EFI crap and install a carb... We're not talking about stone age muscle cars with cable clutches and mechanical speedometers. We're talking about a '90's Japanese supercar. Heck, the 300ZX had a vacuum booster for the clutch hydraulics.

I am very very anti-T56, as you might be able to tell. Plus, if you put any popular cam in a fourth gen with the LS1 and T56, you can't use sixth anymore unless you change the axle ratio, and there goes the 31 mpg on the highway. You should expect a 5.7L LSx to give 27 mpg if you gear it to turn 1800 rpm at 65 mph. That 31 mpg stock is with it geared for 1450 rpm at 65 mph.

If you're camming the engine, you're not concerned about the 31 mpg anyway. I thought the hot ticket in a T56 car (F or Corvette) was a 4.11 rear?

Just because American muscle is using hydraulic clutch release now doesn't mean the old RX7s must be. I still have no clue if RX7 clutch releasing is done by cable or hydraulically or mechanical-linkage. And since I'm not working on one, there's no need for me to learn. But if the RX7 isn't hydraulic, you either have to adapt hydraulics, or you can't use the production T56.
As for gearing, the best gear depends on your powerband, your tire diameter, and what you're doing with your car.
Now, back to watching the build. I was just trying to offer info that I felt was relevant and potentially helpful.

[The Dark Side of Will]

The late '70's and early '80's first gen RX7's (FB's?), I think, had cable clutches.

The FD3 was built from 92ish to 99ish (not offered in the US the whole time) and designed to be a world beating sportscar. It has basically the best of everything and is extremely well designed to be lightweight and stiff. Unlike the 2nd gen RX7, the third gen was not offered as a convertable. The chassis was designed to be only fixed-roof from the get-go, thus it's low weight and high stiffness.

I know that "gearing depends on the application", but almost everybody a few years ago when they were still building LS1's was going to 4.11's in F-bodies and Corvettes. That still works on the street precisely because of the T56's super tall overdrives.

[emod19]

All manual transmission rx7s had hydraulic clutches. Alot of helpful information on v8 rx7 swaps can be found here;

http://www.v8rx7forum.com/forum.php


Steve

[crzyone]

The FD's are absolutely world class sports cars. That takes half the fun out of building them up, though as 3/4 of the work's already done.

Hehe... I'm sure Atilla would love to elaborate, but the state of the Gen III/IV art is such that you could have 600 WHP and daily drivability.

With a light weight chassis like a FD3S, I'd look at a 105mm (~4.125") bore aluminum block with 83mm stroke from a 4.8 litre truck engine. The result is a big bore 5.7. You could put LS7 heads on it with a top shelf valvetrain and run it to 8000.

I really like this idea.

The selection or avaiability here in Canada sucks, I'm basically looking on e-bay and car-part.com for engines. I think I will look for a high mileage or core engine to build instead. Might as well build a fresh motor. What is a large bore block? I suppose I'd have to buy one brand new? Is that an LS7 block?

I love winding engines out, 8000rpm from a sbc sounds like fun. Any other suggestions for a light weight FD?

I won't be buying an engine until September or so, maybe I'll buy a whole LS1 drivetrain and then build the motor over winter.

[AkursedX]

If you're looking for a complete dropout, don't forget to look at dropout's from the GTO's as well. Just a quick hint to expand your search.

[Atilla the Fun]

The best block of all is the LS9 version, but it's not cheap. Any LS3 or L92 block will do. These are way more common, aluminum, they come with 4.065" bores, and can safely go to 4.125".
the best heads come from MAST, they're not cnc'd GM heads, they're entirely new castings that put EVERY other LSx head to shame.
If you're wanting 8000 rpm, you do need the LS9 forged crank and the LS7 titanium rods. Those rods are NOT cheap.

[The Dark Side of Will]

Anyone ever tried it with the 4.8 crank?

Don't forget that the greater main/rod journal overlap makes the 83mm 4.8 crank much stronger than the 92mm cranks. Why pay out the nose for GM titanium rods when there are lots of 4340 rods on the market that will do the job just fine?

[The Dark Side of Will]

I love winding engines out, 8000rpm from a sbc sounds like fun. Any other suggestions for a light weight FD?

TKO instead of T56 will save you 50# or so, but cost in terms of highway RPM.
Tilton instead of full diameter clutch will save rotating mass as well as weight. With the V8 you can have plug/play kits for decent prices.

The Corba diff is aluminum case instead of the FD's iron. I think once you factor in the adaptor subframe, the weight is a wash.